F. Santoyo-gonzalez et al., An efficient synthesis of bis(calix[4]arenes) bis(crown ether)-substitutedcalix[4]arenes, aza-crown calix[4]arenes, and thiaza-crown calix[4]arenes, EUR J ORG C, (21), 2000, pp. 3587-3593
The easy transformation of 5,11,17,23-tetra-tert-butyl-25,27-bis(aminoethox
y)-26,28-dihydroxycalix[4]arene (2) into 5,11,17,23-tetra-tert-butyl-26,28-
dihydroxy-25,27-bis(2-iso-thiocyanoethoxy)calix[4]arene (3) and 5,11,17,23-
tetra-tert-butyl-25,27-bis(chloroacetamidoethoxy)-26 calix[4]arene (4) has
been exploited for the development of an efficient and expeditious synthesi
s of a variety of calix[4]arene derivatives [bis(calix[4]arenes), bis(crown
ether) calix[4]arenes, aza-crown calix[4]arenes, and thiaza-crown calix[4]
arenes]. The functionality of compounds 2 and 3 allowed the formation of in
tramolecular bridges, leading to capped calix[4]arenes (compounds 5, 10, an
d 14) as well as to the construction of double calix[4]arene units by means
of spacers containing thiourea or amide-sulfur groups (compounds 6 and 15,
respectively). In addition, the bis(isothiocyanate) derivative 3 gave acce
ss to a high-yield preparation of heteroditopic bis(crown ether) calix[4]ar
enes (7-9) from commercial amino crown ethers.